Hypodermic syringes have long been in use, and have proven to be an invaluable tool in the prevention and treatment of illness. Due to the use of hypodermic syringes in the treatment of illness, however, and in particular blood related diseases, the need for a hypodermic syringe which can be safely disposed of after use has become increasingly important.
A large portion of the syringes manufactured and sold today are disposable items intended for a single use, after which the syringe is to be disposed of in a safe manner. The conventional disposable hypodermic syringe has a barrel with a first open end and a closed second end, a hypodermic needle extending from the second end and being in fluid communication with the barrel, and a plunger assembly inserted through the open end of the barrel and reciprocable therein for use in drawing fluid through the hypodermic needle and into the barrel, and for forcing fluid from the barrel through the hypodermic needle when giving an injection, for example.
These known disposable hypodermic syringes also include a protective cap or sheath received over the needle and removably secured to the second end of the barrel. After use of the hypodermic syringe, the preferred method of disposal was to place the cap back over the needle on the second end of the syringe barrel, and place the syringe in an appropriate biomedical waste receptacle, or other suitable receptacle provided therefor. However, the placement of the cap back on the second end of the syringe and over the needle requires extreme caution in order to prevent an accidental needle stick in the hand of the person placing the cap back on the syringe. In light of the variety of blood borne illnesses being treated today, to include Hepatitis, and Auto-Immune Disease Syndrome (AIDS), a safer syringe was needed which would prevent accidental needle sticks during handling after use and prior to disposal.
Thus, syringes were developed which had a protective sheath provided coaxially about the barrel of the syringe and movable from a retracted position in which the needle extended or projected from the shield for use, into an extended or locked position in which the shield was moved at least partially about the needle to minimize the risk of accidental needle sticks during handling after use, and in disposal. Numerous hypodermic syringes using safety shields have been developed, among which are those disclosed in U.S. Pat. No. 4,743,233 to Schneider, U.S. Pat. No. 4,874,383 to McNaughton, and in U.S. Pat. No. 5,053,018 to Talonn, et al.
In the patent to Schneider, a safety cap syringe is disclosed which has slidable sleeve positioned on the syringe barrel which is threaded at both of its ends, the second end of the barrel at which the needle is located having a corresponding thread so that the safety cap can be threadably held in an open or retracted position on the barrel. Although Schneider provides a safety cap syringe having a shield movable between a retracted and extended position for at least partially enclosing the needle after use, the patent to Schneider requires that a health professional, or other syringe user, for example, a diabetic, grasp the barrel of the syringe with the fingers of one hand while using the fingers of the other hand to rotate the slidable sleeve for unthreading it from its retracted position, sliding the sleeve forward on the barrel, and then rotating the barrel so that it is threaded into its extended position on the barrel. While preforming these steps, however, the possibility of an accidental needle stick is present, particularly, for example, if the person's hand should slip while trying to rotate and move the sleeve on the syringe.
McNaughton discloses a syringe shield locked in a retracted position on the barrel of the syringe by threads, an elongate guide formed in the barrel of the syringe and having a protrusion extending inwardly from the syringe shield and received therein for guiding the syringe shield along the barrel into the extended position, and a catch or recess for receiving the protrusion to lock the shield into a closed position on the end of the barrel and extending about the needle. Again, and as with the patent to Schneider, after use, the fingers of a person must grasp the barrel of the syringe while the fingers of the other hand are used to once again rotate the barrel, in this instance through a partial quarter turn, then move the shield on the barrel into the extended position, and then once again rotate the shield into a locked position. As with the safety cap syringe of Schneider, therefore, the possibility thus exists that an accidental hand slip or other miscue could result in an accidental needle stick.
Talonn et al. disclose in their patent a combined syringe and needle shield, and a method of manufacture, which once again provides a safety syringe with a needle shield which is movable between a retracted position into an extended position for at least partially enclosing the needle of the syringe after use. To use the syringe of Talonn et al., the needle shield is moved from a retracted position over a series of detents while simultaneously guiding three spaced keys in matched corresponding keyways along the barrel to position the needle shield about the needle. The user then forces the shield into an extended position over a series of stops formed in the collar of the syringe, whereupon the user then grasps the shield and rotates it to lock a spaced series of protrusions formed on the end of the needle shield into a spaced series of slots provided on the collar positioned with respect to the second end of the hypodermic syringe barrel.
Again, and as with the patents to Schneider and McNaughton, the device of Talonn et al. requires that after use of the syringe a person must grasp the barrel of the syringe with the fingers of one hand, grasp the needle shield with the fingers of the second hand, move the needle shield into the extended position, and then rotate the needle shield and ensure that the needle shield clicks or locks into a closed position to ensure that accidental needle sticks are prevented.
None of the patents to Schneider, McNaughton, nor Talonn et al. disclose a needle shield having a cap or end seal formed as an integral part thereof, and which could be moved into a closed position to fully enclose the needle within the safety shield once the safety shield has been moved into its extended or locked position about the needle, thus ensuring that the needle is completely isolated therewithin to prevent the accidental needle stick resulting from a child or other person placing their finger through the otherwise open end of the needle shield and engaging the hypodermic needle therewithin. Moreover, each of the patents to Schneider, McNaughton, and Talonn et al. use a conventional syringe in which a series of indicia or markings are spaced along at least a portion of the length of the barrel for use in measuring the mount of fluid drawn through the hypodermic needle into the barrel of the syringe, i.e., to determine dosage and the like. Thus, the problem arises that the safety shield or needle shield may very well obscure a significant portion of these markings on the barrel of the syringe, or the safety shield must be specially manufactured to allow a health professional or other syringe user to peer through the needle shield to observe the markings on the barrel while also drawing fluid into the barrel, for example a dosage from a vaccine bottle, or blood from a patient, all of which is ordinarily difficult enough without the added distraction of trying to read obscured markings on the barrel of the syringe.
What is needed therefore, but seemingly unavailable in the art, is a hypodermic syringe with a safety shield which can be used quickly and easily in a single one step operation without requiring the unnecessary handling, i.e., rotation of the safety shield while moving the shield into its extended and locked position. What is also needed is an improved hypodermic syringe which is adapted for ease of use as a syringe prior to the time the safety shield is moved into its extended position, and which fully encloses the needle within the safety shield to eliminate the possibility of accidental needle sticks.